Recording medium determining device and recording medium determination method

ABSTRACT

A recording medium determining device includes a light irradiating portion that irradiates a recording medium with visible light; a regular reflection light receiving portion that receives regular reflection light regularly reflected by the recording medium irradiated with light from the light irradiating portion; a diffused reflection light receiving portion that receives diffused reflection light diffusely reflected by the recording medium irradiated with light from the light irradiating portion; and a determining portion that determines the type of recording medium on the basis of each light amount of two or more visible light components with different wavelengths to one another among the light components received by the regular reflection light receiving portion and each light amount of two or more visible light components with different wavelengths to one another among the light components received by the diffused reflection light receiving portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/148,428, filed Jan. 6, 2014, which patentapplication is incorporated herein by reference in its entirety. U.S.patent application Ser. No. 14/148,428 claims the benefit of andpriority to Japanese Patent Application No. 2013-000371, filed Jan. 7,2013, which Japanese patent application is expressly incorporated byreference herein. U.S. patent application Ser. No. 14/148,428 alsoclaims the benefit of and priority to Japanese Patent Application No.2013-268710, filed Dec. 26, 2013, which Japanese patent application isexpressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a recording medium determining deviceand a recording medium determination method that determine, for example,the type of recording medium such as paper, on which an image isrecorded.

2. Related Art

In technologies that record an image on a recording medium such as paperor a resin sheet, there are cases where it is necessary to determine thetype of recording medium used in order to optimize the recordingconditions or a transport form according to, for example, thecharacteristics of the recording medium. There are technologies able tobe used to this end which use the optical characteristics of therecording medium such as disclosed in JP-A-08-314327 andJP-A-2005-315856.

In the technology of the disclosure in JP-A-08-314327, the type ofrecording medium is determined on the basis of the intensity ratio ofthe regular reflection light and diffused reflection light received by alight receiving element along with light from an LED that is a lightemitting element being made incident with respect to a recording medium.In the technology of the disclosure in JP-A-2005-315856, the type ofrecording medium is determined on the basis of each light amount ofregular reflection light and diffused reflection light when the mediumis irradiated with infrared light, and the light amount of a fluorescentcomponent emitted from the recording medium when the medium isirradiated with ultraviolet light.

As types of recording media, there are numerous types in circulation inthe market. Therefore, there is demand for accurately determining thetype thereof; however, the technologies of the related art are unable torespond to such demand. For example, in the technology of the disclosurein JP-A-08-314327, because the determination is simply performed onlywith the intensity ratio of the regular reflection light and thediffused reflection light, a plurality of recording media with similarcharacteristics on this point are unable to be determined. In addition,in the technology of the disclosure in JP-A-2005-315856, although thereflection characteristics with respect to infrared light and thefluorescence characteristics with respect to ultraviolet light are takenas a determination reference, according to the findings described laterof the inventors of the present application, the difference between thereflection characteristics of various recording media with respect toinfrared light is extremely small, furthermore, the fluorescence withrespect to ultraviolet light is mainly due to a brightening agent, anddetermination of the type of recording medium not including abrightening agent is unable to be made.

SUMMARY

An advantage of some aspects of the invention is to provide a technologyable to more accurately determine various types of recording media.

According to an aspect of the invention, there is provided a recordingmedium determining device including a light irradiating portion thatirradiates a recording medium with visible light; a regular reflectionlight receiving portion that receives regular reflection light regularlyreflected by the recording medium irradiated with light from the lightirradiating portion; a diffused reflection light receiving portion thatreceives diffused reflection light diffusely reflected by the recordingmedium irradiated with light from the light irradiating portion; and adetermining portion that determines the type of recording medium on thebasis of each light amount of two or more visible light components withdifferent wavelengths to one another among the light components receivedby the regular reflection light receiving portion and each light amountof two or more visible light components with different wavelengths toone another among the light components received by the diffusedreflection light receiving portion.

According to another aspect of the invention, there is provided arecording medium determination method, including irradiating a recordingmedium with visible light; receiving regular reflection light in whichirradiated light is regularly reflected by the recording medium;receiving diffused reflection light in which irradiated light isdiffusely reflected by the recording medium; and determining the type ofrecording medium on the basis of each light amount of two or morevisible light components with wavelengths different to one another amongthe light components received in receiving the regular reflection light,and each light amount of two or more visible light components withwavelengths different to one another among the light components receivedin receiving the diffused reflection light.

According to the aspects of the invention, the type of recording mediumis determined on the basis of the light amount of each of two or morevisible light components among the regular reflection light and thediffused reflection light from the recording medium. Moreover, accordingto the aspects of the invention, although the determination may beperformed using two or more light components from each of the regularreflection light and the diffused reflection light, the light componentused in the regular reflection light and the light component used in thediffused reflection light may be the same or may be different.

Although described in detail later, according to new findings by theinventors of the present application, the reflection characteristicswith respect to incident light for each type of recording medium varymore greatly in the visible region than in the infrared region, andfurther, the wavelength dependence of the reflection characteristics inthe visible region differ greatly according to the type of recordingmedium. Using this, according to the aspects of the invention,determination of the recording medium is performed using the lightamount of two or more wavelengths in each of regular reflection lightand diffused reflection light. Therefore, it is possible to determinenumerous types of recording medium with higher accuracy than in therelated art.

According to the aspects of the invention, for example, the recordingmedium is preferably irradiated with light not substantially includingultraviolet rays. According to the aspects of the invention, since thetype of recording medium is determined on the basis of thecharacteristics of regular reflection and diffused reflection of visiblelight incident on the recording medium, detection errors of the lightamount due to mixed incidence of light components occurring due tofluorescence may be reduced by light not substantially includingultraviolet rays being made incident.

In addition, at least one of the visible light components of thediffused reflection light used in the determination, for example, may bea wavelength that corresponds to blue or green. In addition, at leastone of the visible light components of the regular reflection light usedin the determination may be a wavelength component that corresponds toblue. According to the findings of the inventors of the presentapplication, the variance in reflection characteristics for each type ofrecording medium, for example, is more remarkable in the shortwavelength components such as blue or green than in the long wavelengthcomponents such as red. Accordingly, it is possible to determine thetype of recording medium with higher accuracy by using the shortwavelength components in the determination.

In addition, according to the aspects of the invention, the recordingmedium is irradiated with light including two or more visible lightcomponents with wavelengths different to one another, and the lightamount of each light component may be obtained by separating each of theregular reflection light and the diffused reflection light. By doing so,reflection light of each light component may be received at the sametime, and the determination process may be performed in a short time. Inorder to achieve the advantage, for example, the light which therecording medium is irradiated with is set to white light, and a lightreceiving element provided with an RGB color filter that separatesincident light into each of the R (red), G (green) and B (blue)components may be used.

Alternatively, for example, the recording medium is preferablyirradiated by switching between two or more types of visible light withspectral distributions different to one another. In this case, regularreflection light and diffused reflection light are received by a lightreceiving element not having a color separation function, and theactions and effects according to the aspects of the invention may beobtained. In addition, it becomes easy to individually set the intensityof incident light for each light component, and it is possible toimprove detection precision by expanding the dynamic range in the lightamount detection.

In addition, the ratio of the light amount of regular reflection lightfrom the recording medium and the light amount of regular reflectionlight from a predetermined reference reflection portion, and the ratioof the light amount of diffused reflection light from the recordingmedium and the light amount of diffused reflection light from apredetermined reference reflection portion is preferably obtained. In sodoing, the reflectivity (described in detail later) which is the ratioof the reflected light from the reference reflection portion and thereflection light from the recording medium may be obtained. Therefore,even in a case in which there are variations in the characteristics ofthe light irradiating portion that irradiates a recording medium withlight and the light receiving portion that receives reflection light, itis possible to stably perform determination according to determinationin light of the reflectivity.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a diagram showing the spectral distribution of diffusedreflection light in various recording media.

FIG. 2 is a diagram showing the spectral distribution of diffusedreflection light when light including ultraviolet light is incident.

FIGS. 3A to 3C are diagrams showing one example of a specificconfiguration of a determining device according to an aspect of theinvention.

FIGS. 4A and 4B are diagrams showing an example of spectral sensitivitycharacteristics of a light receiving portion.

FIG. 5 is a diagram showing one example of a binary tree obtained fromknown reflection data.

FIG. 6 is a diagram showing a combination of wavelength components forwhich the recording medium is determinable.

FIGS. 7A and 7B are diagrams schematically showing a configuration of acontroller for performing a recording medium determination process.

FIG. 8 is a flowchart showing one example of a recording mediumdetermination process that is executed by the controller.

FIGS. 9A to 9C are lateral cross-sectional diagrams showing a morespecific configuration of a determining device.

FIG. 10 is a flowchart showing a determination process operationincluding calibration.

FIGS. 11A to 11C are diagrams showing another example of a specificconfiguration of a determining device according to an aspect of theinvention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Initially, the findings of the inventors of the present application thatare the basis of the aspects of the invention and the principles of theaspects of the invention of the present application based thereupon willbe described. The inventors of the present application researched thespectral distribution of regular reflection light and diffusedreflection light when a recording medium is irradiated with light fornumerous types of recording medium in circulation in the market. Sincewhile the regular reflection light that is light reflected by thesurface of the recording medium reflects the state of the surface of therecording medium, diffused reflection light is light that is emittedagain by being scattered in the interior of the recording medium, thecharacteristics of the material of the recording medium are betterreflected.

FIG. 1 is a diagram showing the spectral distribution of diffusedreflection light in various recording media. In more detail, FIG. 1 is adiagram showing an example of a portion of the results of measuring thespectral distribution of light diffusely reflected by the recordingmedium when various recording media are irradiated with white light froma tungsten light source. Moreover, in FIG. 1, the ratio of the reflectedlight amount from the recording medium and the reflected light amountfrom a reference plate when irradiation light is made incident on apredetermined white reference plate is denoted as “reflectivity”.Accordingly, in a material with a higher reflectiveness than thereference plate, there are cases where the reflectivity exceeds 1.Variations occur in the light amount received and identified by lightreceiving portion from the light irradiated by the irradiating portionaccording to the irradiation amount of the irradiating portion, thelight receiving conditions of the light receiving portion, and the like.Therefore, by obtaining the ratio between the time in which the lightamount of reflection light from the recording medium is obtained and thelight amount of reflection light obtained from the reference plate inthe same conditions in which the irradiation portion and the lightreceiving portion are combined, it is possible to stably confirm thereflection state of the recording medium.

The irradiation light is white light from a tungsten light source whichincludes almost no components from a wavelength of 370 nm or lower to awavelength of 400 nm or lower, or, as shown in FIG. 3C described later,is white light with high color rendering properties having a peak ineach of the short wavelength side and the long wavelength side whilesubstantially evenly including a visible region including almost nocomponents with a wavelength of 400 nm or less and a wavelength of 700nm or more (generally, a wavelength range of from 400 nm to 750 nm). Theinventors of the present application obtained the following findings byperforming spectrometry of the diffused reflective light by such lightbeing made incident on the recording medium.

That is, as shown in FIG. 1, there is wavelength dependence in thereflectivity of the diffused reflection due to the recording medium andthe value of the reflectivity in each wavelength differs greatlyaccording to the type of recording medium. In particular, while eachrecording medium shows characteristic reflectivity in the shortwavelength region of generally a wavelength from 400 nm to 500 nm, andthe medium wavelength region of generally a wavelength from 500 nm to600 nm, the variance in reflectivity for each recording medium iscomparatively small in the long wavelength region of generally awavelength of 600 nm or higher.

From this, it is understood that rather than simply detecting the lightamount of the overall diffused light, the reflection light amount isseparately detected for each wavelength component, and by combining andevaluating the values thereof, there is a possibility of being able tomore finely identify the differences in the reflection characteristicsof the recording media caused by differences in the material than in therelated art.

That is, by using the reflection light intensity of two or morewavelength components with different wavelengths to one another fromamong the diffused reflection light in which incident light is diffuselyreflected by the recording medium, it is possible to determine numeroustypes of recording medium with higher accuracy than the related art. Inthis case, it is desirable that the incident light not includeultraviolet light components, and the reason therefor is as below.

FIG. 2 is a diagram showing the spectral distribution of diffusedreflection light when light including an ultraviolet light component ismade incident on the recording medium. When light including anultraviolet light component is incident on the recording medium, becausefluorescent light excited by a fluorescent brightening agent included inthe recording medium appears in the short wavelength region in additionto components in which the incident light is reflected, the apparentreflectivity in the short wavelength regions increases. Therefore, in amiddle wavelength region and a long wavelength region, variance in thereflectivity caused by the type of recording medium becomes ratherinconspicuous. Naturally, there is a little fluorescence excited byultraviolet light in a recording medium not including a fluorescentbrightening agent.

In this way, ultraviolet light components being included in the incidentlight, while emphasizing the variance for each recording medium inspecified wavelength components, reduces the variance for each recordingmedium in other wavelength components. This becomes an obstruction inthe technical conception of the aspects of the invention which is todetermine the type of recording medium from the reflection light amountin two or more wavelengths. In addition, in the reflection lightdetected, the light components originally included in the incident lightand the fluorescent light components excited by ultraviolet light aremixed in an indistinguishable state, and it is difficult to detect onlythe pure diffused reflection light component. The technical concept ofthe aspects of the invention is to specify the type of recording mediumby ascertaining to what extent light components included in the incidentlight are reflected (regular reflection and diffused reflection) by therecording medium, and is not intended to detect light generatedsecondarily by the recording medium through light irradiation. Fromthese reasons, it is desirable that the light incident on the recordingmedium not contain ultraviolet light components that excite fluorescentlight. Naturally, it is permissible to include minute ultraviolet lightcomponents in a range that does not influence the measurement in thevisible range.

As above, it is possible to determine the material of numerous recordingmedia by detecting the light intensity of two or more wavelengthcomponents included in the diffused reflection light. Meanwhile, even ifthe materials of the base material of the recording media are the same,the type is distinguished through differences in the surface working,and it is possible for the differences in surface working to bedetermined by the light intensity of the regular reflection light.

Since the spectral distribution of regular reflection light is, inprinciple, substantially the same as the spectral distribution ofincident light, it is possible to determine the surface state of arecording medium if the light intensity of specified wavelengthcomponents of the regular reflection light is able to be detected. Thatis, if the light intensity of two or more wavelength components includedin the diffused reflection light and the light intensity of at least onewavelength component included in regular reflection light are obtained,it is possible in principle to specify the type of recording medium.However, in experiments by the inventors of the present applicationusing dozens of types of recording media available on the market, it wasdetermined that it is desirable to use the values of the reflectionlight intensity of two or more wavelength components for the regularreflection light in order to accurately determine these recording media.In other words, even in the reflection light intensity of regularreflection light, some wavelength dependence is visible.

Based on the findings, according to an aspect of the invention, thelight intensity of two or more wavelength components for each of theregular reflection light and the diffused reflection light areseparately obtained and determination of the type of recording medium isperformed on the basis of the results thereof. More specifically, usingthe light intensity of each wavelength component thus obtained and adetermination reference set on the basis of optical characteristicsobtained in advance for a plurality of types of recording medium, it isdetermined to which of known recording media the recording medium thatis a determination target corresponds. By doing so, it is possible todetermine numerous types of recording medium with high accuracy.

FIGS. 3A to 3C are diagrams showing one example of a specificconfiguration of a determining device according to an aspect of theinvention. The determining device 100 determines the type of recordingmedium by being mounted to various image recording apparatuses, such asa printing device, copy machine or printer. The printing method thereofis not particularly limited, and is applicable to various methods, suchas a transfer method, an ink jet method, or an electrophotographicmethod.

In the determining device 100 in the configuration example shown in FIG.3A, a light source device 110 is provided above a platen 140 in which areference reflection plate 141 having predetermined reflectioncharacteristics is embedded. It is desirable that the referencereflection plate 141, as shown by an example of reflectioncharacteristics in FIG. 3B, be a material with a white surface havinggenerally constant and comparatively high (for example, 0.75 or higher)reflectivity in the visible light region of 400 nm to approximately 750nm. It is possible to use a sintered compact or a ceramic of a powdersuch as titanium nitride, barium sulfate or aluminum oxide, or a whiteplastic, for example, an aggregate or foamed material of a powder suchas an acrylic resin or a polycarbonate resin as the reference platehaving such reflection characteristics. Furthermore, the reference platemay have a coating layer such as glass on the surface thereof in orderto prevent abrasion or fouling of the surface or to adjust the degree ofgloss.

When “reflectivity” of a recording medium is used in the followingdescription, the term is defined as the value of the ratio of the lightamount of reflection light detected in the recording medium and thelight amount of reflection light detected in advance in a referencereflection plate 141. The “reflectivity” of a recording medium thusdefined is not easily influenced by variations in individualcharacteristics and changes over time in the light source andcontributes to improvements in the determination precision. Moreover, itis desirable that a calibration in which reflection light from thereference reflection plate 141 is detected again be executed, asappropriate.

The light source device 110 includes a light source portion 111 thatemits light having a predetermined spectral distribution and intensity,a light collecting portion 112 that collects emitted light from thelight source portion 111, and a diaphragm portion 113 that regulates theradiation direction of the collected light. The light source device 110irradiates light towards the reference reflection plate 141 on theplaten 140 from diagonally above. The incidence angle θ1 on thereference reflection plate 141 of light from the light source device 110is preferably 30 degrees to 60 degrees, and may be set to, for example,45 degrees.

It is possible to use white light having the spectral distribution shownin FIG. 3C, for example, as the irradiation light herein, and it ispossible to use a white LED, for example, as the light source portion111. Although a discharge lamp such as a xenon arc lamp or anincandescent lamp such as a halogen lamp may be used as a light source,and in this case, in order for the ultraviolet light component to bereduced, it is desirable that a filter that removes the wavelengthcomponents of 380 nm or less, and more preferably 400 nm or less, beused.

A regular reflection light detecting device 120 is arranged on theoptical path of light emitted from the light source device 110 andregularly reflected by the reference reflection plate 141. That is, theangle anticipated by the regular reflection light detecting device 120for the reference reflection plate 141 is substantially equal to theincident angle θ1. The regular reflection light detecting device 120receives regular reflection light from the reference reflection plate141 and outputs a signal according to the received light amount.

Meanwhile, a diffused light detecting device 130 that receives diffusedreflection light from the reference reflection plate 141 is provided ata position that anticipates the reference reflection plate 141 at anangle θ2 greater than the incident angle θ1. It is possible for theangle θ2 to be, for example, 90 degrees.

The regular reflection light detecting device 120 includes a lightreceiving portion 121 that outputs a signal according to the receivedlight amount for each component in which light is received and separatedinto several wavelengths, and a diaphragm portion 122 that controls thedirection of light incident on the light receiving portion 121.Similarly, the diffused light detecting device 130 includes a lightreceiving portion 131 and a diaphragm portion 132. It is possible forthe regular reflection light detecting device 120 and the diffused lightdetecting device 130 to use the same configuration as one another.

FIG. 4A is a diagram showing an example of spectral sensitivitycharacteristics of a light receiving portion. FIG. 4B is a diagramshowing an example of spectral sensitivity characteristics of a lightreceiving portion. In the example in FIG. 4A, the incident light isseparated into blue (B) component with a wavelength of 400 nm toapproximately 540 nm (center wavelength 460 nm), a green (G) componentwith a wavelength of 480 nm to approximately 600 nm (center wavelength540 nm), and a red (R) component with a wavelength of 590 nm toapproximately 720 nm (center wavelength 620 nm to 660 nm). In addition,in the example in FIG. 4B, the spectral sensitivity of the R componentis enlarged to the infrared region, and the bandwidth thereof is 590 nmto 1200 nm (center wavelength 620 nm to 720 nm). These are therepresentative characteristics of RGB color filters that are inpractical use, and it is possible to use a general color CCD sensor orcolor CMOS sensor or the like as a light receiving portion having suchspectral sensitivity characteristics. Therefore, it is possible tosuppress the device costs to be low.

Description of the configuration of the determining device continues byreturning to FIGS. 3A to 3C. In addition to each of the aboveconfigurations, a controller 150 that executes a determination processof a recording medium along with governing the operations thereof isprovided in the determining device 100. In the determining device 100configured as above, when a recording medium M that is the determinationtarget is arranged on the platen 140, light is irradiated from the lightsource device 110, regular reflection light therefrom is received by theregular reflection light detecting device 120, whereas diffusedreflection light is received by the diffused light detecting device 130.The regular reflection light detecting device 120 and the diffused lightdetecting device 130 separate received light into components of each ofthe RGB colors, and respectively output signals according to thereceived light amount for each component with respect to the controller150.

The controller 150 determines the type of recording medium M on thebasis of the value of the light amount of two or more wavelengthcomponents among each of the RGB components of the regular reflectionlight detected by the regular reflection light detecting device 120, andthe value of the light amount of two or more wavelengths among each ofthe RGB color components of the diffused reflection light detected bythe diffused light detecting device 130. Next, the recording mediumdetermination process using the controller 150 will be described.

In the recording medium determination process using the controller 150,reflection data for regular reflection and diffused reflection isobtained in advance for each of the RGB color components for a pluralityof types of recording medium that may be determination targets. Then,when the recording medium M to be determined is provided, the lightamount of regular reflection light and diffused reflection light aredetected for each of the RGB color components for the recording mediumM, the detected values thereof are compared to those of known recordingmedia, and it is determined that the recording medium with the closestcharacteristics and the recording medium M are the same type.

It is possible to perform various methods of comparing and contrastingthe recording medium M that is the determination target and the knownrecording medium, and the characteristics of the recording medium M arepreferably analyzed using learning data that is machine learned in lightof reflection characteristic data of the known recording media, and therecording medium having characteristics close to the recording medium Mis selected using a known multivariate analysis technique. Here, as aprocessing example applied to computer processing, description of anexample of determination using a binary tree analysis structured on thebasis of known reflection data.

FIG. 5 is a diagram showing one example of a binary tree obtained fromknown reflection data. In the example, thirteen types among the variouscommercially available recording media, specifically three types ofordinary paper (ordinary paper 1 to 3), three types of photographicpaper (photographic paper 1 to 3), three types of art paper (art paper 1to 3), three types of matte paper (matte paper 1 to 3) and one type oftransparent OHP sheet for ink jet printing, were selected, and werestructured in a binary tree for distinguishing each recording mediumusing reflectivity data for regular reflection and diffused reflectionmeasured for each of the RGB color components in the media. Moreover,since methods of structuring a binary tree from sample data are known,description thereof will not be made here.

In the drawing, the references Sg and Sb indicate the value of thereflectivity of regular reflection light in the green (G) and blue (B)components respectively, and the references Dr and Dg indicate thevalues of the reflectivity of diffused reflection light in the red (R)and green (G) components respectively. In addition thereto, there is thereflectivity of the red component in regular reflection light and of theblue component in the diffused reflection light as the reflectivitydata, and below these values are represented by the references Sr and Dbrespectively.

The reflectivity is obtained from the light amount of each componentdetected in the recording medium M that is a determination target, andit is possible to determine the type of the recording medium M byperforming analysis using a structured binary tree. More specifically,at each node of the binary tree, one designated value from the obtainedreflectivity data is selected and compared to the reference value,searching is performed towards the lower layer while selecting one childaccording to the magnitude relationship thereof. In so doing, any of thethirteen types of recording medium defined as “leaves” of the binarytree is finally arrived at and is set as the determination results. Inthe example, as a result of structuring the binary tree usingreflectivity data obtained with each recording medium it is possible tomore reliably determine the thirteen types of recording medium from thereflectivity Sg and Sb of the two color components of regular reflectionlight and the reflectivity Dr and Dg of the two color components ofdiffused reflection light.

In this way, not all of the reflectivity data for the three colorcomponents of each of the regular reflection light and the diffusedreflection light are necessary at all times. In addition, the tree shapeof the binary tree shown in FIG. 5, the type of reflection lightcomponent used in the analysis, and the numerical value of thereflectivity are considered to be naturally different according to thecombination of recording media for which data is acquired in advance.However, according to the results of trials by the inventors of thepresent application performed while making various changes to thecombination of reflectivity data that is applied to the process foraround thirty types of commercially available recording medium, it wasunderstood that the two or more wavelength components for regularreflection light and the two or more wavelength components for diffusedreflection light are necessary for accurate determination. That is, thecombination of the light intensity of a plurality of wavelengthcomponents in which the reflection light are different to one anotherdiffers according to the type of recording medium, and is necessary inorder to determine the type of recording medium.

FIG. 6 is a diagram showing a combination of wavelength components forwhich the recording medium is determinable. As shown in the drawing,although it is natural that reliable determination is possible if all ofthe RGB components of each of the regular reflection light and thediffused reflection light are used, it is understood that reliabledetermination is possible even if only two color components are usedfrom each of the regular reflection light and the diffused reflectionlight. From the results, it is understood that it is preferable that theblue component in the regular reflection light be used in determination,and further, preferable that blue and green components in the diffusedreflection light be used, and furthermore, preferable that the bluecomponent and green component be included together among the four typesof the two regular reflection light components and the two diffusedreflection light components.

In this way, when determining the type of recording medium by detectingregular reflection light and diffused reflection light of the visiblelight with which the recording medium is irradiated, it is possible toperform the determination with high accuracy by using the reflectionlight intensity of the blue component and green component withcomparatively short wavelengths from the visible range. This isconsistent with the variance in the reflection characteristics of eachtype of recording medium shown in FIG. 1, that is, the reflection lightamount for each recording medium being small in the short wavelengthband and comparatively large in the long wavelength band. Accordingly,it is desirable that the irradiation light include a large amount ofcomponents with short wavelengths to long wavelengths, that is the bluecomponent and green component, from the visible range. However, sinceinclusion of a fluorescent light component excited by the ultravioletlight component included in the irradiation light is a cause ofdetermination errors, it is desirable that the irradiation light belight not substantially including an ultraviolet light component or fromwhich the ultraviolet light component is removed in advance. A white LEDwith high color rendering properties may be suitably used as a lightsource towards this advantage.

Moreover, as described above, determination of the type of recordingmedium is able to be performed on the basis of the light amountdetection results of two or more wavelength components of each of theregular reflection light and diffused reflection light. Accordingly,separating the received reflection light into three components (RGB) isnot a necessary condition. However, even in a case in which all threecolor components are not used in the determination, it is desirable thatthe device have a color separation function for the three colors. Thefirst reason is that if the combination of the plurality of types ofrecording medium that is the determination target changes, there is apossibility for the color component used in the determination to alsochange. The second reason is that optical devices having a colorseparation function for the three colors are currently easily available,and there is a possibility of being able to suppress the device costs tobe lower than preparing hardware for extracting only two wavelengthcomponents.

FIG. 7A is a diagram schematically showing a configuration of acontroller for performing a recording medium determination process. FIG.7B is a diagram showing an example of a database array in thecontroller. More specifically, FIG. 7A is a diagram showing aconfiguration example of a controller 150, and FIG. 7B is a diagramshowing a data structure example of a determination database arrayprovided in the controller 150. As shown in FIG. 7A, a CPU 151 thatexecutes various processes, and a determination database array 152 as areference data saving destination that the CPU 151 references in thedetermination process are provided in the controller 150. Thereflectivity data Sr, Sg, and Sb for each color component of the regularreflection light output from the regular reflection light detectingdevice 120, and the reflectivity data Dr, Dg, Db of each color componentof the diffused reflection light output from the diffused lightdetecting device 130 are input to the CPU 151. The CPU 151 executes therecording medium determination process using the reflectivity data thusprovided and the determination database array 152.

The determination database array 152, as shown in FIG. 7B, includes adetermination database formed from a plurality of sets of determinationdata groups, and a medium database formed from a plurality of mediumdata groups.

The determination database corresponds to the binary tree in FIG. 5 as acomputer processing simple data structure, and is formed from a numberof sets of determination data corresponding to the number of nodes inthe binary tree. One set of determination data in the determinationdatabase includes information related to the type of reflection lightdata used in a branching decision at a node in the binary tree(determination reflection light type) and the threshold value thereof(determination reference data), and information related to a jumpdestination in the determination database array 152 for each of whenbranching conditions are satisfied and when not satisfied (a jumpdestination when conditions are satisfied and a jump destination whenconditions are not satisfied). In addition, a flag indicating whetherthe determination process continues or finishes is further included. Inthe determination data, the flag is uniformly set to a value indicating“NO”.

The medium database includes a number of sets of medium datacorresponding to the number of types of recording medium registered inadvance, and each item of medium data includes a unique title thatdiscriminates each recording medium (recording medium type name), andthe processing conditions when the recording medium is provided to theprinting process, for example, transport conditions or parameters suchas image density (printing parameters). In addition, a flag indicatingwhether the determination process continues or finishes is furtherincluded. In the medium data, the flag is uniformly set to a value thatindicates “YES”.

FIG. 8 is a flowchart showing one example of a recording mediumdetermination process that is executed by the controller. Initially, thevalue of a pointer indicating a reference address in the determinationdatabase array is set to the header address of the determinationdatabase array (Step S101). Next, the determination data of thedesignated address is read from the determination database (Step S102).

Subsequently, the value of a determination finish flag from the readdata is determined (Step S103). Since the flag in each item ofdetermination data in the determination database is set to “NO”, thedetermination result at this time is “NO”, and Step S104 is executednext. That is, determination reference data from the determinationdatabase and the determination reflection light type are acquired (StepsS104, S105). Then, one item specified according to the determinationreflection light type from the measured reflectivity data in thereflection light from the recording medium M is selected (Step S106),and the value thereof and the determination reference data acquired fromthe determination database are compared (Step S107).

Here, while in a case in which the condition of “(measurementdata)<(reference data)” is satisfied (Yes in Step S107), the pointer isupdated to the jump destination when conditions are satisfied indicatedby the determination data (Step 109), in a case in which the conditionsare not satisfied (NO in Step S107), the pointer is updated to the jumpdestination when conditions are not satisfied (Step S108). Thereafter,the database is newly read by returning to Step S102.

At this time, if the jump address designated by the pointer is in thedetermination database, the above process is repeated on the basis ofthe designated determination data. This indicates that the branchingdecision progresses one layer deeper in the binary tree. Meanwhile, ifthe jump destination designated by the pointer is in the mediumdatabase, the data subsequently read out is the medium data. In themedium data, since the determination finish flag is set to “YES”, thedetermination in Step S103 proceeds to Step S110 by becoming “YES”, andthe process ends by acquiring the recording medium type name and theprinting parameters from the medium data designated by the pointer. Thisindicates that the search along the binary tree arrives at a “leaf”, andthe type of recording medium corresponding to the leaf is obtained asthe determination result.

In a printing apparatus or the like equipped with the determining device100, it is possible to use the recording medium type name acquired asthe determination results for notifying a user, for example, of thedetermination results. In addition, in a case in which the printingprocess to be executed and the recording medium do not match, it ispossible to use applications such as performing a warning notificationor pausing the printing process. In addition, it is possible to use theprinting parameters read out from the medium database, for example, forachieving optimization of the processing conditions of the printingprocess.

FIG. 9A is a lateral cross-sectional diagram showing a more specificconfiguration of a determining device. FIG. 9B is a lateralcross-sectional diagram showing a more specific configuration of adetermining device. FIG. 9C is a lateral cross-sectional diagram showinga more specific configuration of a determining device. A light sourceunit 11, a regular reflection light receiving unit 12 and diffused lightreceiving unit 13 corresponding respectively to the light source device110, the regular reflection light detecting device 120 and the diffusedlight detecting device 130 of the above-described determining device 100are included in the determining device 10 shown in FIG. 9A, and theseare accommodated in the housing 16 that is a cavity in which theinterior having an opening in the lower surface functions as themeasurement space SP. The housing 16 prevents disturbance due to straylight or the like by irradiation and reflection of light being performedin an internal cavity, while holding the positional relationship betweeneach unit.

Although it is normally preferable that the inner wall surface 16 a ofthe housing 16 that faces the measurement space SP be matte black, whiteor a mirror finish may also be used. Moreover, as shown in FIG. 9B, ahousing 18 may be used in which an inner surface wall 18 a has asemi-circular cross-sectional shape. In addition, as shown in FIG. 9C,an aperture diaphragm 19 may be provided on the lower surface of thehousing 16 in order to prevent mixing of reflection light from thesurface of the platen 14 a other than the reference reflection plate 14b.

A platen 14 a is arranged below the determining device 10, and thereference reflection plate 14 b is fitted to a through hole opened in apart thereof. These correspond to the previously described platen 140and reference reflection plate 141.

In addition, the housing 16 is held to freely move up and down by ahousing elevating mechanism 17. That is, a lift arm 17 a that extendsupward is attached to the upper portion of the housing 16 and the liftarm 17 a moves up and down accompanying the operation of an elevationdriving portion 17 b using, for example, a solenoid. Therefore, byoperating the elevation driving portion 17 b, the housing 16 moves toapproach and separate with respect to the platen 14 a by moving up anddown. In a state in which the housing 16 is furthest lowered, the lowersurface of the housing 16 comes into contact with the upper surface ofthe platen 14 a, either directly or via the recording medium M arrangedon the platen 14 a. In so doing, it is possible to prevent outside lightfrom infiltrating to the measurement space SP.

The light source unit 11 includes a white LED 11 a with high colorrendering properties that is an irradiation light source, a condenserlens 11 b in which the irradiated light therefrom is collected, anemission diaphragm 11 c that restricts the emission direction of thecollected light. In addition, the regular reflection light receivingunit 12 includes a light sensor 12 a that receives regular reflectionlight from the reference reflection plate 14 b or the recording medium,and an entrance diaphragm 12 b that restricts the incident light to thelight sensor 12 a. Similarly, the diffused reflection light receivingunit 13 includes a light sensor 13 a that receives diffused reflectionlight from the reference reflection plate 14 b or the recording medium,and an entrance diaphragm 13 b that restricts the incident light to thelight sensor 13 a.

FIG. 10 is a flowchart showing a determination process operationincluding calibration of the determining device. Firstly, before therecording medium is arranged on the platen 14 a, the determining device10 is lowered by the housing elevating mechanism 17, and the lowersurface of the housing 16 enters a state of being in tight contact withthe upper surface of the platen 14 a (Step S201). In this state, the LED11 a that is an irradiation light source emits light, and light amountadjustment is performed such that the light amount is suitable andstable in the measurement (Step S202).

In this state, the regular reflection light and the diffused reflectionlight from the reference reflection plate 14 b are received by theregular reflection light receiving unit 12 and the diffused reflectionlight receiving unit 13, and the received light amount is obtained foreach of the RGB color components. The values thereof are acquired asreference values when the reflectivity of the recording medium isobtained (Step S204). By acquiring the reflection light from thereference reflection plate 14 b as a reference value, it is possible toobtain stable determination results regardless of variations in thecharacteristics of the light source and light receiving portion, orchanges therein over time. That is, acquisition of the reference valueshere has the meaning of calibration of the determining device. Then, thereceived light amount of each component is determined (Step S205), andwhen a predetermined value set in advance is not reached, since anabnormality of the determining device is suspected, the process finisheswith an error.

If each received light amount is normal, the determining device 10 istemporarily separated from the surface of the platen 14 a by beingraised by the housing elevating mechanism 17 (Step S206), and the lowersurface of the housing 16 enters a state of tight contact with the uppersurface of the recording medium M by the determining device 10 beinglowered again (Step S208) after the recording medium that is adetermination target is transported to the determination positiondirectly below the determining device 10 (Step S207). In this state,light is irradiated toward the surface of the recording medium M, andmeasurement of the regular reflection light and the diffused reflectionlight is performed (Step S209).

Then, although the recording medium determination process is performedon the basis of the measurement results (Step S210), the processingcontent is the same as shown in FIG. 8. When the type of recordingmedium is determined in this way, the determining device 10 is separatedfrom the recording medium M by being raised (Step S211), the recordingmedium is discharged (Step S212) and the process ends.

FIG. 11A is a diagram showing another example of a specificconfiguration of a determining device according to an aspect of theinvention. FIG. 11B is a diagram showing another example of a specificconfiguration of a determining device according to an aspect of theinvention. FIG. 11C is a graph showing the relationship betweenreflectivity and wavelength. In the determining device 200 of theconfiguration example shown in FIG. 11A, light from the light sourcedevice 210 is irradiated with respect to the recording medium M arrangedon the platen 240 in which the reference reflection plate 241 isprovided. The light source device 210 includes a light source portion211 that emits light having a plurality of wavelengths, a lightcollecting portion 212 that collects the emitted light from the lightsource portion 211, a diaphragm portion 213 that regulates the radiationdirection of the collected light, and a filter 214 through which onlypredetermined wavelength components from the light emitted through thediaphragm portion 213 selectively pass. The filter 214 is able to switchthe wavelength of light that has passed through. That is, in thedetermining device 200, it is possible for the spectral distribution oflight with which the recording medium M is irradiated to be changed byswitching the filter 214.

In the determining device 300 of the configuration example shown in FIG.11B, light from the light source device 310 is irradiated with respectto the recording medium M arranged on the platen 340 in which thereference reflection plate 341 is provided. The light source device 310includes a light source portion 311 able to switch the wavelength ofemitted light, a light collecting portion 312 that collects emittedlight from the light source portion 311, and a diaphragm portion 313that regulates the radiation direction of the collected light. It ispossible to use a multicolor LED in which, for example, light emittingelements for each of the RGB colors are assembled in one package as thelight source portion 311. That is, in the determining device 300, by theemission light components from the light source portion 311 beingchanged, it is possible for the spectral distribution of the light withwhich the recording medium M is irradiated to be changed.

Even in these configurations, the regular reflection light and thediffused reflection light are received for each wavelength component andthe light amount detection results thereof are provided in thedetermination of the type of recording medium M. However, in contrast tothe white light including a plurality of wavelength components at thesame time being separated on the light receiving side by beingirradiated on the recording medium M in the configuration example ofFIGS. 3A to 3C, in these aspects, the wavelength components of light arealready limited at the stage where the light is incident on therecording medium. Accordingly, as the light receiving portion receivingreflection light, in addition to being usable similarly to a lightreceiving portion having a light separating function as shown in FIGS.3A to 4B, for example, it is possible to use a light receiving elementhaving sensitivity with respect to a broad bandwidth of light, as shownin FIG. 11C. It is possible to use photoconductive cells and the likeusing a semiconductor sensor, a photomultiplier tube, and aphotoconductive material such as cadmium sulfide, as such a lightreceiving element.

As an advantage due to the combination of light source portion able toswitch the wavelength of incident light in this way and a lightreceiving element not having a color separating function, it is possibleto individually set the incident light amount for each wavelengthcomponent. As shown in FIG. 1, the variance of the reflection lightamount for each type of recording medium, in other words, the dynamicrange in the light amount measurement differs greatly according to thewavelength of light. In the experiments by the inventors of the presentapplication, as understood from FIG. 1, the long wavelength side in thevisible range, in other words, the dynamic range in the red regionbecomes smaller. Therefore, for example, if the light intensity of thered color component of the incident light is made greater than the othercolor components, more high precision detection is possible by expandingthe dynamic range of the red color component during measurement, and itis possible to increase the accuracy of the determination.

For example, in a recording medium such as a dark sheet in which theground color is significantly distant from white, the short wavelengthcomponent included in the reflection light is reduced, and the redcomponent and the infrared component are somewhat increased. Therefore,it is possible to more precisely detect the variance in the reflectioncharacteristics for each type of recording medium and performdetermination with high accuracy by expanding the dynamic range of thewavelength band.

If the reflection light amount for two or more wavelength components foreach of the regular reflection light and the diffused reflection lightis obtained, it is possible to determine the type of recording medium inthe same manner as above by using the values thereof.

As above, in the embodiments of the determining device according to theaspects of the invention, the recording medium is irradiated withvisible light, and the light amount of two or more wavelengths for eachof the regular reflection light and the diffused reflection light areindividually detected. Then, the detection results of the reflectionlight amount of the two or more wavelength components in the regularreflection light and two or more wavelength components in the diffusedreflection light are used, and if the recording medium that is adetermination target corresponds to any of the plurality of recordingmedia for which the characteristics are known in advance is determined.Through doing so, it is possible to perform determination with only thetotal light amount of the regular reflection light and the diffusedreflection light, and to determine with high accuracy more types ofrecording medium than in the related art that performs determination onthe basis of the reflection light of fluorescent light excited byultraviolet rays or the reflection light in the infrared region.

In the experiments by the inventors of the present application, aplurality of sheets for each of approximately 30 types recording mediumtotaling approximately 150 sheets were determined, and it was confirmedthat the type was correctly determined with 100% probability.

In this determination method, either of the light source and the lightreceiving portion are able to be configured by a device that operates inthe visible light range. Since numerous products are in practical use assuch devices, by appropriately selecting from among these, it ispossible to configure the determining device according to the intendeduse, cost or the like.

As described above, in this embodiment, the determining devices 10 and100 correspond to the “recording medium determining device” of theaspects of the invention, the light source devices 110, 210, and 310function as the “light irradiation portion” of the aspects of thepresent invention, and the regular reflection light detecting device 120and the diffused light detecting device 130 respectively function as the“regular reflection light receiving portion” and the “diffusedreflection light receiving portion” of the aspects of the invention. Inaddition, the controller 150 functions as the “determining portion” ofthe aspects of the invention, and the reference reflection plate 141functions as the “reference reflection portion” of the aspects of theinvention.

Moreover, the aspects of the invention are not limited to the aboveembodiments, and various modifications other than those described aboveare possible as long as not departing from the gist thereof. Forexample, in the above-described embodiments, a binary tree structured onthe basis of reflectivity data acquired from known recording media, andthe type thereof is determined from reflectivity data acquired with therecording medium that is a determination target. However, the essence ofthe aspects of the invention is performing determination using the lightamount value of two or more wavelength components of each of the regularreflection light and the diffused reflection light, and there is noparticular limit on the content of the calculation process fordetermination using these values.

In addition, although the reflection light is separated using an easilyobtainable RGB color filter in the above embodiments, how manywavelength components the reflection light is separated into and whichwavelength components are used are arbitrary and not limited to theabove.

In addition, in the above-described determining device 10 and therecording medium determination process using the same, the determiningdevice 10 comes into tight contact with the recording medium. Althoughthis is to prevent infiltration of external light while allowing theoptical axis of the regular reflection light from the light sourcedevice to the regular reflection light receiving device to bestabilized, the elevation device is preferably not included according tothe usage. For example, a case in which there is no influence ofexternal light by the determining device being arranged inside the caseof a printing apparatus, corresponds thereto. In addition, in the caseof a configuration that separates and contacts the determining deviceand the recording medium (or a support portion of the recording medium),the recording medium (or a support portion of the recording medium) maymove.

In addition, in the above embodiments, although determination isperformed by arranging the determining device above the recording mediumarranged on a planar platen, the positional relationship of therecording medium and the determining device is not limited thereto, and,for example, the determining device may be provided laterally withrespect to a recording medium transported in the vertical direction, andfurther, the determining device is preferably arranged on the lowersurface side of the recording medium arranged horizontally. Moreover, inaddition to a configuration in which the recording medium is arranged ona planar platen, the configuration which may detect reflection light byperforming light irradiation with respect to the surface of a recordingmedium pressed by a guide member and the surface of a curved recordingmedium that is wound around a roller may be used.

In addition, stopping the recording medium during determinationprocessing is not necessary, and the configuration which may detectreflection light by performing light irradiation with respect to thesurface of a recording medium that is being transported and moved at apredetermined transport speed may be used.

What is claimed is:
 1. A recording medium determining device comprising:a light irradiating portion that irradiates a recording medium withlight; a regular reflection light receiving portion that receivesregular reflection light regularly reflected by the recording mediumirradiated with light from the light irradiating portion; a diffusedreflection light receiving portion that receives diffused reflectionlight diffusely reflected by the recording medium irradiated with lightfrom the light irradiating portion; and a determining portion thatdetermines the type of recording medium on the basis of light intensityof at least one wavelength component included in the light componentsreceived by the regular reflection light receiving portion and lightintensity of two or more wavelength components included in the lightcomponents received by the diffused reflection light receiving portion.2. The recording medium determining device according to claim 1, whereinthe light with which the recording medium is irradiated notsubstantially including the light components with a wavelength of 400 nmor less.
 3. The recording medium determining device according to claim1, wherein the light with which the recording medium is irradiated notsubstantially including the light components with a wavelength of 700 nmor more.
 4. The recording medium determining device according to claim1, further comprising a filter that removes part of the wavelengthcomponents of an irradiation light.
 5. The recording medium determiningdevice according to claim 1, wherein the wavelength component of theregular reflection light used by the determining portion in thedetermination corresponds to blue.
 6. The recording medium determiningdevice according to claim 1, wherein the light irradiating portionirradiates the recording medium with light including two or more lightcomponents with wavelengths different to one another, and the regularreflection light receiving portion and the diffused reflection lightreceiving portion obtain the light amount of each light component byseparating incident light.
 7. The recording medium determining deviceaccording to claim 1, wherein the light irradiating portion irradiatesthe recording medium by switching between two or more types of lightwith spectral distributions different to one another.
 8. The recordingmedium determining device according to claim 1, further comprising areference reflection portion irradiated with light from the lightirradiating portion, wherein the determining portion obtains a ratio ofa light amount of regular reflection light from the recording medium anda light amount of regular reflection light from the reference reflectionportion received by the regular reflection light receiving portion, anda ratio of a light amount of diffused reflection light from therecording medium and a light amount of diffused reflection light fromthe reference reflection portion received by the diffused reflectionlight receiving portion.
 9. A recording medium determination method,comprising: irradiating a recording medium with light; receiving regularreflection light in which irradiated light is regularly reflected by therecording medium; receiving diffused reflection light in whichirradiated light is diffusely reflected by the recording medium; anddetermining the type of recording medium on the basis of light intensityof at least one wavelength component included in the light componentsreceived in receiving the regular reflection light, and light intensityof two or more wavelength components included in the light componentsreceived in receiving the diffused reflection light.